1. Technical Field
The present disclosure relates generally to ultrasonic surgical instruments. More specifically, the present disclosure relates to ultrasonic surgical instruments having an end effector configured to effect tissue dissection, cutting, coagulation, ligation and/or hemostasis, which instrument can be used in open as well as laparoscopic or endoscopic surgical procedures.
2. Background of Related Art
The use of ultrasonic instruments for surgical procedures including dissecting, cutting, ligating, effecting coagulation in, and/or effecting hemostasis in tissue and the benefits associated therewith are well known. For example, the use of an ultrasonic generator in conjunction with a surgical scalpel facilitates faster and easier cutting of organic tissue. Furthermore, heat generated by frictional contact between the scalpel blade and the body tissue, as the scalpel blade is vibrated at a high frequency, accelerates blood vessel clotting in the area of the cut, i.e., accelerates coagulation. The speed of heat generation is controlled by two factors, namely the frequency of the oscillations generated by the system, (determined by the manufacturer), and the amplitude or distance of movement of the oscillations as the blade is moved (determined by the user).
Advantages associated with ultrasonic surgical instruments include minimal lateral thermal damage, speed, absence of creation of an electrical circuit through the patient, and absence of unwanted byproducts such as smoke. Ultrasonic surgical instruments are suitable for traditional open surgical procedures and are particularly suitable for minimally invasive surgery such as laparoscopic and endoscopic surgery.
An ultrasonic surgical instrument typically includes a manipulatable structure, such as a hand piece, having an ultrasonic transducer connected to an end-effector, such as a cutting/coagulating blade, via a vibration coupler that conducts ultrasonic frequency longitudinal vibrations from the ultrasonic transducer to the end-effector.
The ultrasonic displacements, i.e., amplitude of the vibrations transmitted from the transducer to the end-effector are sinusoidal by nature. The sinusoidal motion of the vibrations of the blade is a limiting factor that constrains the effective length of the blade. At the points along the sinusoidal curve where the amplitude is equal to zero, there is zero motion of the blade. To avoid areas of zero motion along the blade, a blade shorter than ½ wavelength of the oscillations is used. Currently the maximum blade length of a blade without zero motion areas is approximately 0.250″.
Alternatively, a longer blade is used having areas of maximum motion, as well as areas of no motion along the length of the vibrating blade. The areas of no motion decrease the effective length of the blade, decreasing efficiency of the blade, and thus undesirably increasing the time needed to complete the surgical procedure.
Furthermore, there are large variations in amplitude along the length of the blade due to the sinusoidal nature of the oscillations, resulting in inconsistent behavior of the blade, and a lack of uniform operative results along the length of the blade. Uniformity is desirable for an even rate of cutting and coagulation, allowing the surgeon to proceed with the cutting procedure at an even rate and providing the surgeon with the ability to reliably predict results of operation of the surgical device.
Accordingly, the need exists for a decrease in operative time by increasing efficiency of the end-effector by increasing the effective length of the end-effector by reducing zero points along the sinusoidal amplitude curve. Furthermore, there is a need for increased consistency of behavior of the end-effector for obtaining uniform operative results along the length of the end-effector. Finally, the need exists for an ultrasonic surgical instrument configured using Micro Electrical Mechanical Systems (MEMS) technology in which the instrument is reduced in size and weight while increasing the effective length and behavior consistency of the end effector.